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SubjectRe: NETIF_F_SG question
> On Sun, 2 Feb 2003 02:39:41 +0100, Joakim Tjernlund <> wrote:
> >
> > I think HW checksumming and SG are independent. Either one of them should
> > not require the other one in any context.
> They should be independent in general, but they aren't when the particular
> case of TCP/IPv4 is concerned.
> > Zero copy sendfile() does not require HW checksum to do zero copy, right?
> Wrong...
> > If HW checksum is present, then you get some extra performance as a bonus.
> You get zerocopy, yes. :-) No HW cksum, no zerocopy.

OK, but it should be easy to remove HW cksum as a condition to do zerocopy?

> Don't let this stop you, however. It's always possible that other networking
> stacks will eventually make use of SG while not requiring HW TCP/UDP cksums.
> None of them do right now, but...

zerocopy without requiring HW cksums only OR could for instance the forwarding
procdure also benefit from SG without requiring HW cksums?

> > (hmm, one could make SG mandatory and the devices that don't support it can
> > implement it in their driver. Just an idea)
> Not really, that way lies driver madness. The less complexity in the driver,
> the better.

Just a wild idea, forget it. You are right

> Ion
> [starfire driver maintainer]
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